It is previously known apparatuses for extruding plastic deformable or pulverulent materials (semimoist) which have been prepared for the purpose for the production of extrudates of different kinds, such as raw materials, or end products for the pharmaceutical, food, or feed-stuff industries, as well as for the production of fertilizers and other organic and inorganic products.
Hitherto known apparatuses having been used for extrusion said materials are to be compared with meat mincing-machines, where the material by means of one or more screws is fed and pressed up to and through an aperture disc, which can be axially or radially arranged. Already the physical action of the screws makes this method irrational and provides for shearing forces in the material with accompanying heating effects, which in most cases are destructive. Furthermore, the material is graded into a solid/liquid phase prior to the aperture disc, which results in an inhomogenous product. The pressure force needed according to this method is further applied onto the whole area of the aperture disc, which after a short time leads to a deformation of the aperture disc. This deformation is particularly annoying at aperture diameters of 1 mm and less, when the screen (aperture disc) by deformation goes away from the screw(-s) and the forming effect of these, which means that the load has to be further increased.
The disadvantage of this known technique for extruding plastic deformable or pulverulent materials prepared for the purpose is as mentioned above that too high a temperature is built up during too long a period which in many cases means a destruction, or at least a serious risk for destruction of the material fed, particularly when organic material is present. Also inorganic materials can, however, change, e.g., by release of chemically bound water, which can completely change the chemical and physical properties of the product at hand.
Demands have thus been brought forward requesting a device and a process which provides for the production of an extrudate of heat- and pressure sensitive materials for obtaining well formulated extrudates by extrusion, while avoiding temperature increasing compression and pressure forces during a substantial time period, within the material.